Runey responded to someone earlier with the simple fact that Autumn was the last main character added (another will come eventually), so she has the least amount of events at the moment.
Personally I'm glad you found it a bit fast. Myself, I see it as very well built up to, but almost everyone is constantly nagging Runey to have us fuck her already, which if you've met Autumn at all, you know why we can't yet :P
Basically though, she has been somewhat strictly repressed by her family and religion, while being a very smart and curious person. She also has biological desires like anyone else, but because she's open minded enough to wonder why things are, when those barriers break down, she embraces experimenting.
Hell, she mentioned at the beach a while earlier that she wants to keep doing lewd things, and even suggested specific ones she's interested in trying.
I'm really proud of how she handled the Exhibition stuff, she oozed confidence. Now this big lore stuff is just fascinating, and she was given good reason to be in the position she's at.